Flexible and stretchable sheet material useful in forming protective and decorative coatings

ABSTRACT

A flexible and stretchable sheet material that is capable of being stretched to conform to a three-dimensional substrate to form a protective and decorative coating thereon is comprised of a thin flexible support having adhered thereto a protective and decorative layer such as a paint layer comprising a colorant incorporated in a film-forming binder. Both the support and the protective and decorative layer are characterized by a very high degree of thickness uniformity and the sheet material exhibits a high level of surface uniformity, an ability to undergo substantial elongation, and a substantially uniform quality and appearance; whereby it can be stretched and bent in the process of bonding it to a substrate and still achieve a defect-free coating of uniformly attractive appearance. 
     A process for the manufacture of the sheet material comprises the steps of: 
     providing a flexible support sheet; 
     providing a fluid protective and decorative film-forming composition; 
     forming a laminar flow of the composition and directing the flow into contact with the surface of the support to form thereon a protective and decorative layer of substantially uniform thickness; and converting the protective and decorative layer to a dry and tack-free state. 
     In one preferred embodiment, the protective and decorative layer comprises a film-forming binder, a colorant and generally flat light-reflecting particles which are effectively oriented by the laminar flow process to provide a layer characterized by a high degree of geometric metamerism.

This is a divisional of copending application Ser. No. 07/609,050 filedon Nov. 2, 1990 which is a continuation of Ser. No. 07/116,426 filed onNov. 3, 1987 and now abandoned.

FIELD OF THE INVENTION

This invention relates in general to the art of providing protective anddecorative coatings of the type most typically applied in industry byspray painting techniques. More specifically, this invention relates toa flexible and stretchable sheet material that can be bonded to varioussubstrates, including exterior automotive panels, to achieve desiredprotective and decorative effects and thereby reduce or eliminate theneed to utilize spray painting processes in the manufacturing operation.The invention also relates to a process for manufacturing such sheetmaterial on an industrial scale.

BACKGROUND OF THE INVENTION

To facilitate an understanding of the many advantages of the inventionand to provide for ease of description, the invention will bespecifically described hereinafter with reference to providingprotective and decorative coatings on exterior automotive panels, but itshould be understood that the automobile is only one of many differenttypes of products in whose manufacture the invention can be beneficiallyapplied.

As pointed out in an article by Alan J. Backhouse entitled "Routes ToLow Pollution Glamour Metallic Auomotive Finishes", Journal of CoatingsTechnology, Vol. 54, No. 693, pages 83-90, October 1982, there is agrowing need to reduce the amount of atmospheric pollution caused bysolvents emitted during industrial paining processes. Many differentapproaches to meeting this need have been proposed. For example, effortshave been made to replace the solvent-based paints typically used forautomobiles with water-based paints. As another alternative, work hasbeen done to facilitate the use of high solids formulations which willresult in proportionately less emission of organic solvents. However,the application of automotive finishes is a highly demanding art becauseof the extremely high quality of the surface finish required and becauseof the very common application of metallic finishes to provide whatBackhouse refers to as "high stylistic effects". Accordingly, pastefforts to replace the low viscosity, low-solids-content paintformulations conventionally used in spray painting operations in theautomotive industry have met with only very limited success.

A much more promising approach to solving the problem is to eliminateentirely the need for spray painting operations to provide the necessaryprotective and decorative coating on exterior automotive panels.Elimination of spray painting, or a substantial reduction in the extentof its use, would not only be environmentally beneficial in reducingatmospheric pollution, but would be extremely beneficial from a costsavings standpoint in that spray painting operations are wasteful of thepaint to such an extent that more than half of the paint may be lost aswaste material. A means for achieving such goal exists through the useof a pre-formed thermoplastic sheet material which can be glued orotherwise securely bonded to the panel to provide the protective anddecorative coating. Such techniques are well known and widely used inindustry, and have been utilized for such purposes as interiorautomobile panels as described, for example, in U.S. Pat. No. 3,551,232issued Dec. 29, 1970. This art is summarized in the aforesaid patent inthe following words:

"It is present day conventional practice to make structural membersconsisting of a relatively rigid substrate to which is bonded as asurface or cover layer a synthetic resin sheet. The surface layer may besmooth or embossed and may be suitably colored to provide a desireddecorative effect. The substrate may be formed of a relatively rigidsynthetic resin, such as polystyrene, or sheet metal, and the surfacelayer and the substrate are bonded together to form a laminate. Suchstructures may be used for a variety of purposes such as interiorautomobile panels, glove compartment doors, and the like.

A convenient and economical method for making such articles involves theapplication of a suitable adhesive to the surface of the substrate andthen vacuum forming the decorative cover layer over the adhesive layerof the substrate".

The objective of U.S. Pat. No. 3,551,232 is to overcome the problems ofbubbling and blistering of the resin sheet that tend to occur in thevacuum-forming process. It achieves this by use of an adhesivecontaining an inert particulate filler which minimizes the entrapment ofair.

To employ a process of the type described in U.S. Pat. No. 3,551,232with exterior automotive panels presents a much greater challenge. Thesurface appearance of such panels is of critical importance, so that itis necessary not only to avoid such problems as bubbling or blisteringcaused by entrapped air, but to provide a protective and decorativecoating that will equal or exceed in many respects, the quality of aspray-painted surface and that is equally capable of providing the "highstylistic effects" that are of growing importance in the automotivemarketplace. Furthermore, exterior automotive panels present aparticular problem in view of the great difficulty of smoothly adheringa flexible sheet material to a substrate which may possess complexcurvature and the even greater difficulty of doing so while maintainingover the entire surface of the panel a uniform degree of the colorintensity exhibited by the coating.

Heretofore, efforts have been made to produce a flexible and stretchablesheet material having these capabilities through the application of oneor more paint layers to the surface of a thermoformable polymericsupport. However, such efforts have, prior to this invention, beenunsuccessful in that the sheet material has suffered from variousdefects which have rendered its commercial use impractical. Thus, forexample, prior efforts have resulted in products which exhibit numerouscoating defects and in which the paint layer does not have the highdegree of uniformity which permits the sheet material to undergo thesevere stresses of the thermoforming process and yet provide a productwhich meets the exacting quality standards of an exterior automotivefinish.

It is toward the objective of providing a flexible and stretchable sheetmaterial which is capable of being stretched to conform to athree-dimensional substrate, such as an exterior automotive panel, toprovide a high quality defect-free protective and decorative coating ofuniformly attractive appearance, that the present invention is directed.

SUMMARY OF THE INVENTION

In accordance with this invention, it has been found, most unexpectedly,that a flexible and stretchable sheet material that is (1) capable ofmeeting the demanding requirements of an exterior automotive finish and(2) capable of withstanding the stretching and bending forces involvedin the process of bonding it to exterior automotive panels, can beproduced through exacting control of the thickness and thicknessuniformity of the support combined with the use of precision coatingtechniques to provide exacting control of the thickness and thicknessuniformity of the coatings. Moreover, as hereinafter described, suchcoating techniques provide essentially defect-free coatings having acontinuous substantially uniform quality and appearance.

The sheet material of this invention comprises a thin flexible supportsheet and a protective and decorative layer adhered to one surface ofthe support sheet. The support has heat-softening and tensile elongationproperties which adapt it to use in the thermoforming process and theprotective and decorative layer has heat softening and tensileelongation properties that are compatible with those of the support soas to permit symmetrical elongation, whereby the sheet material canundergo substantial elongation by the application of stretching forceswithout crazing of the protective and decorative layer nor delaminationof the protective and decorative layer from the support. The sheetmaterial has a substantially unstressed relaxed state and a relaxed areaand is heat softenable to a substantially plastic state in which it isplastically expandable and formable over irregular surfaces to anextended state having an extended area up to at least 50% greater thanthe relaxed area. The protective and decorative layer has asubstantially uniform quality and appearance both in the relaxed andextended states of the sheet material. The sheet material can bestretched to conform to a three-dimensional substrate and bonded theretoto achieve a smooth and wrinkle-free protective and decorative coatingof uniformly attractive appearance.

The invention also provides a process for the manufacture of the sheetmaterial comprising the steps of: providing a thin, flexible supportsheet; providing a fluid protective and decorative film-formingcomposition; forming a laminar flow of the composition and directing theflow into contact with the surface of the support to form thereon aprotective and decorative layer of substantially uniform thickness; andconverting the protective and decorative coating to a dry and tack-freestate. The protective and decorative film-forming composition isadvantageously coated on the support having thereon anadhesion-promoting tie-layer. The process of this invention provides anessentially defect-free coating with a high degree of uniformity oflayer thickness and a substantially uniform quality and appearance.

In a very important embodiment of the invention, the protective anddecorative layer is a paint layer comprising a film-forming binder, acolorant and generally flat light-reflecting particles which areeffectively oriented by the laminar flow process of this invention, thatis, they are preferentially oriented substantially parallel to thesurface of the coating. This provides a layer characterized by a highdegree of geometric metamerism.

In another important embodiment of the invention, the sheet materialincludes a topcoat comprising a crosslinked polymer and the support,paint layer and topcoat layer have heat-softening and tensile elongationproperties which render the sheet material suitable for use in athermoforming process and which are mutually compatible so as to permitsymmetrical elongation, whereby the sheet material can undergosubstantial elongation by the application of stretching forces withoutcrazing or delamination of the paint and topcoat layers, and thesupport, paint and topcoat layers are of sufficiently uniform characterthat the sheet material exhibits substantially the same uniformity ofappearance before and after the thermoforming process.

In another embodiment of this invention, there is provided a structuralelement comprising a three-dimensional substrate having securely bondedto at least one surface thereof in a uniform wrinkle-free state aprotective and decorative coating formed from the flexible andstretchable sheet material described above.

In a further embodiment of the invention, a method of applying aprotective and decorative coating on a three-dimensional substrateincludes the steps of heating and stretching the above-described sheetmaterial as it is brought into conforming association with at least onesurface of the substrate and securely bonding it to the substrate toform thereon a smooth and wrinkle-free protective and decorativecoating.

In yet another embodiment of the invention, there is provided a methodof molding a shaped article and simultaneously providing such articlewith a protective and decorative coating formed from the above-describedsheet material on at least one surface thereof.

As explained hereinafter, the sheet material of this invention isadapted for use in a thermoforming process in which it is elongated andis especially advantageous in providing essentially defect-free coatingsof continuous substantially uniform quality and appearance both in therelaxed and extended states of the sheet material.

Other advantageous features will become readily apparent upon referenceto the following description of the preferred embodiments when read inlight of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic side elevational view of an apparatus usablefor manufacturing the sheet material of the present invention;

FIG. 2 is an enlarged cross-sectional elevational view of a sheetmaterial manufactured in accordance with the present invention;

FIG. 3 is a top plan view of a predetermined area of a sheet materialconstructed in accordance with the present invention;

FIG. 4 is a view similar to FIG. 3 after the sheet material has beenextended up to 21/2 times in area; and

FIG. 5 is a partial cross-sectional view of a coating containing lightreflecting particles that have been oriented in accordance with thepresent invention.

FIG. 6 is a metal particle histogram illustrating relative orientationsfor particles oriented in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with this invention, it has been unexpectedly discoveredthat the many difficult problems inherent in fabricating a flexible andstretchable sheet material that is adapted for use in a thermoformingprocess in which it is stretched to conform to a three-dimensionalsubstrate and bonded thereto so as to form a smooth and wrinkle-freeprotective and decorative coating exhibiting "high stylistic effects"can be effectively obviated by the sheet material of this invention.Such sheet material has been found, most surprisingly, to produce afinished product with a protective and decorative coating that is freeof distortion such as ripples, wrinkles, kink marks, and the like andthat exhibits an appearance at least equal in overall quality to thatachievable by spray coating.

This invention is based at least partly on the recognition that aflexible and stretchable sheet material can provide a protective anddecorative coating on articles of three-dimensional shape that possessesproperties at least as good as that achievable by spray painting, whileavoiding many of the disadvantages associated with spray paintingprocesses. In a particularly preferred embodiment, the invention isbased on the further recognition that such sheet material can meet theexacting demands of the automotive industry for very high qualityexterior automotive finishes. Being capable of meeting the stringentdemands of the automotive industry, the sheet material of this inventionis, of course, also suitable for use in many other less demandingapplications and is readily adaptable for use with a very wide varietyof substrates, to which it can be attached by an adhesive or by beingintegrally bonded thereto by techniques such as heat fusion.

The precision coating capability provided by the laminar flow process ofthis invention permits the formation of a protective and decorativelayer which is essentially defect free. Moreover, it enables theexacting control of layer thickness which--coupled with close control ofsupport thickness--permits the manufacture of a flexible sheet materialthat is capable of meeting both the demands of the vacuum-forming andthermoforming processes and the rigorous demands imposed in meetingindustry standards for the appearance and performance of automotivefinishes. Close control of the physical properties of the flexible andstretchable sheet material of this invention is the key to itssuccessful utilization. Such properties can be obtained with the use ofa very wide diversity of different materials, both in regard to thesupport and in regard to the protective and decorative layer andoptional layers such as a tie-layer, a topcoat layer and an adhesivelayer. A detailed description of particularly useful materials for thesupport and for each of these layers is provided hereinbelow.

The sheet material of this invention comprises a thin flexible supportsheet. The support sheet preferably comprises an essentially planar,self-supporting, stretchable, thermoplastic polymeric film. The supportcan be transparent, translucent or opaque. If desired, it can be matchedin color to the color of the protective and decorative layer byincorporation therein of a suitable pigment. This is often beneficial inthat a scratch which extends through the light-reflecting layer will beless noticeable if the support is of the same color. The support has asubstantially uniform thickness. Preferably, the support has a meanthickness Ts in the range of from about 0.05 to 0.40 millimeters. Apreferred mean thickness is in the range of from about 0.16 to 0.32millimeters. Support thickness is measured by standard thickness tracingtechniques known to those skilled in the art. Alternatively, supportthickness and thickness deviation can be readily determined fromcross-sectional photomicrographs of the sheet material. Supportthickness is measured both across the support width and in a directionperpendicular to the width, in a length about equal to the supportwidth. Ts is herein defined as the average of the mean thicknessmeasured in both directions. The maximum support thickness deviation,ts, is herein defined as the maximum thickness minus the minimumthickness of the support from the thickness measurements taken asdescribed above. The support preferably satisfies the relation ts<0.20Ts. Accordingly, the support exhibits a high degree of widthwise andlengthwise thickness uniformity. Highly preferred supports have amaximum thickness deviation which satisfies the relation ts<0.10 Ts. Thethickness uniformity of the support contributes to the uniformlyattractive defect-free appearance of the sheet material.

Suitable materials for the support sheet include stretchablethermoplastic polymeric films having heat softening and tensileelongation properties which adapt it to use in the thermoformingprocess. Preferred are those films known to be useful in thermoformingand/or vacuum-forming techniques, such as polyvinyl chloride, polyvinylacetate, ABS (acrylonitrile-butadiene-styrene) resins, polyethylene andpolypropylene. Useful support materials include the polyarylate blendswith copolyesters described in U.S. Pat. No. 4,246,381, and thecopolyesters derived from aromatic polyesters and glycol polyestersdescribed in U.S. Pat. No. 4,287,325. Blends of rubber-modifiedstyrene-maleic anhydrides with polycarbonates and/or polyesters are alsouseful, as are blends of poly(ether-esters) and polyesters. Particularlypreferred support materials exhibit a tensile elongation at break of atleast about 40% when measured in accordance with ASTM D-638. A highlypreferred support material is a blend of copolyesters based onpoly(1,4-cyclohexylenedimethylene terephthalate) and rubber-modifiedstyrene-maleic anhydride copolymers as described in U.S. Pat. No.4,582,876. Such support consists of a blend of (a) 70 to 30 weightpercent copolyester consisting of repeating units from terephthalicacid, repeating units from 1,4-cyclohexanedimethanol present in theamount of 25 to 90 mole % and repeating units from a second glycolhaving 2 to 6 carbon atoms present in the amount of 75 to 10 mol %,wherein the total mol % of glycol is equal to 100 mol %, and (b) 30 to70 weight percent thermoplastic rubber-modified vinyl aromatic polymercompositions comprising (1) from 60 to 93% by weight of a nonequimolarcopolymer of 70 to 98% by weight based on a copolymer of a vinylaromatic monomer and from 2 to 30% by weight based on a copolymer of anunsaturated dicarboxylic acid moiety copolymerizable therewith, and (2)from 7 to 40% by weight of at least two differing rubbery additiveswhich were present during the copolymerization of the monomers ofcomponent (1), wherein the rubbery additives comprise from 5 to 20% byweight based on the total composition of at least one high vinylaromatic conjugated diene copolymer wherein the at least one highconjugated diene-vinyl aromatic copolymer comprises from about 60 toabout 93% by weight of the conjugated diene. At least one high vinylaromatic conjugated diene copolymer preferably is a block copolymerwhich comprises a greater amount of vinyl aromatic than conjugated dienemonomer. The support can include fillers, UV absorbers, plasticizers,colorants, antioxidants, etc. known to be useful in polymeric films.

The sheet material of this invention includes a protective anddecorative layer such as a paint layer on one surface of the support.The paint layer, which is also referred to herein as a basecoat layer,preferably comprises a colorant incorporated in a film-forming binder.Conventional colorants used in surface coating compositions can beemployed, including inorganic pigments such as titanium dioxide, ironoxide, chromium oxide, lead chromate, carbon black, silica, talc, chinaclay, metallic oxides, silicates, chromates, etc., and organic pigments,such as phthalocyanine blue, phthalocyanine green, carbazole violet,anthrapyrimidine yellow, flavanthrone yellow, isoindoline yellow,indanthrone blue, quinacridone violet, perylene reds, diazo red andothers known to those skilled in the art.

The film-forming binder can comprise any of the film-forming resinsconventionally used as binders in basecoat compositions. Particularlyuseful resinous binders are acrylic polymers, polyesters, includingalkyds, and polyurethanes. Examples of such binders and methods for thepreparation thereof are described in U.S. Pat. Nos. 4,681,811; 4,403,003and 4,220,679.

The acrylic polymers are copolymers of one or more alkyl esters ofacrylic acid or methacrylic acid optionally together with one or moreother polymerizable ethylenically unsaturated monomers. These polymersmay be either of the thermoplastic type or thermosetting crosslinkingtype. Suitable alkyl esters of acrylic acid or methacrylic acid includemethyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylacrylate, butyl acrylate and 2-ethylhexyl acrylate. Suitable othercopolymerizable ethylenically unsaturated monomers include vinylaromatic compounds such as styrene and vinyl toluene; nitriles such asacrylonitrile and methacrylonitrile; vinyl and vinylidene halides suchas vinyl chloride and vinylidene fluoride and vinyl esters such as vinylacetate.

Where the polymer is of the crosslinking type, suitable functionalmonomers may be used in addition to the other acrylic monomers mentionedabove and include, for example, acrylic acid, methacrylic acid,hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropylacrylate, and hydroxypropyl methacrylate. The coating composition insuch cases contains a crosslinking agent such as a condensate of anamine or an amide with formaldehyde such as urea, melamine, orbenzoguanamine reacted with formaldehyde or a lower alkyl ether of suchcondensate in which the alkyl groups contain from 1 to 4 carbon atoms.Other crosslinking agents such as polyisocyanates including blockedpolyisocyanates may be also used. Also, the acrylic polymer can beprepared with N-(alkoxymethyl)acrylamides andN-(alkoxymethyl)methacrylamides which result in self-crosslinkingacrylic polymers.

The acrylic polymer may be prepared by solution polymerizationtechniques in the presence of suitable catalysts such as organicperoxides or azo compounds, for example, benzoyl peroxide orN,N'-azobis-(isobutyronitrile). The polymerization can be carried out inan organic solution in which the monomers are soluble. Suitable solventsare aromatic solvents such as xylene and toluene and ketones such asmethyl amyl ketone. Alternately, the acrylic polymer may be prepared byaqueous emulsion or dispersion polymerization techniques.

Besides acrylic polymers, the resinous binder for the paint compositionmay be an alkyd resin or a polyester. Such polymers may be prepared in aknown manner by condensation of polyhydric alcohols and polycarboxylicacids. Suitable polyhydric alcohols include ethylene glycol, propyleneglycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol,diethylene glycol, glycerol, trimethylolpropane, and pentaerythritol.

Suitable polycarboxylic acids include succinic acid, adipic acid,azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid,tetrahydrophthalic acid, hexhydrophthalic acid, and trimellitic acid.Besides the polycarboxylic acids mentioned above, functional equivalentsof the polycarboxylic acids such as anhydrides where they exist or loweralkyl esters of the polycarboxylic acids such as the methyl esters maybe used.

Where it is desired to produce air-drying alkyd resins, suitable dryingoil fatty acids may be used and include those derived from linseed oil,soya bean oil, tail oil, dehydrated castor oil or tung oil.

The polyesters and preferably the alkyd resins contain a portion of freehydroxyl and/or carboxyl groups which are available for furthercrosslinking reaction. Suitable crosslinking agents are the amine oramide-aldehyde condensates or the polyisocyanate curing agents asmentioned above.

Polyurethanes can also be used as the resinous binder of the paintlayer. Among the polyurethanes which can be used are polymeric polyolswhich are prepared by reacting the polyester polyols or acrylic polyolssuch as those mentioned above with a polyisocyanate such that the OH/NCOequivalent ratio is greater than 1:1 so that free hydroxyl groups arepresent in the product.

The organic polyisocyanate which is used to prepare the polyurethanepolyol can be an aliphatic or an aromatic polyisocyanate or a mixture ofthe two. Diisocyanates are preferred, although higher polyisocyanatescan be used in place of or in combination with diisocyanates.

Examples of suitable aromatic diisocyanates are 4,4'-diphenylmethanediisocyanate and toluene diisocyanate. Examples of suitable aliphaticdiisocyanates are straight chain aliphatic diisocyanates such as1,6-hexamethylene diisocyanate. Also, cycloaliphatic diisocyanates canbe employed. Examples include isophorone diisocyanate and4,4'-methylene-bis-(cyclohexyl isocyanate). Examples of suitable higherpolyisocyanates are 1,2,4-benzene triisocyanate and polymethylenepolyphenyl isocyanate.

Most of the polymers prepared as described above are organicsolvent-based polymers, although acrylic polymers can be prepared viaaqueous emulsion polymerization techniques and used as aqueous-basedbasecoat compositions. Water-based basecoats in color plus-clearcompositions are disclosed in U.S. Pat. No. 4,403,003, and the resinouscompositions used in preparing these basecoats can be used in thepractice of this invention. Also, water-based polyurethanes such asthose prepared in accordance with U.S. Pat. No. 4,147,679 can be used asthe resinous binder in the paint layer herein.

The resinous binder for the paint layer can also be the resinous binderused in formulating the clear topcoat composition described below.

Preferred paints of those described above have been used on externalautomobile components of deformable urethanes. Such paints stretch anddeform without cracking or delaminating when the urethane is deformed.

The paint layer preferably has a mean thickness Tr in the range of fromabout 0.012 to 0.080 millimeters. A particularly preferred meanthickness is in the range of from about 0.020 to 0.060 millimeters. Themaximum thickness deviation tr of the paint layer preferably satisfiesthe relation tr<0.15 Tr. More preferably, tr satisfies the relationtr<0.10 Tr. Thickness and thickness deviation of the paint layer can bereadily determined from cross-sectional photomicrographs of the sheetmaterial. As noted, the thickness uniformity of both the support andpaint layer are believed to be important in providing defect-freecoatings of uniformly attractive appearance.

The heat softening and tensile elongation properties of the paint layermust be compatible with those of the support so as to permit symmetricalelongation. By symmetrical elongation it is meant that the sheetmaterial can undergo substantial elongation by the application ofstretching forces without splitting or crazing of the paint layer nordelamination of the paint layer from the support. Applicant's inventivesheet material provides outstanding symmetrical elongation, whichresults in part from the thickness and thickness uniformity of thelayers. The ratio of the mean thickness of the paint layer to the meanthickness of the support preferably is in the range of 1.00 to 0.04 andmore preferably in the range of 0.50 to 0.08. A particularly preferredratio is about 0.02. Sheet materials having thickness ratios of about0.2 prepared as described below have been found to provide substantialsymmetrical elongation without splitting, crazing or delamination.

It should be noted that the thermoforming process typically involvesstretching in all directions rather than just a longitudinal stretchingof the sheet material. Thus, the sheet material is extended in area.Prior to thermoforming, the sheet material can be said to be in arelaxed state in which it is substantially unstressed. By thethermoforming process, it is softened to a substantially plastic stateand plastically extended to an extended state. The sheet material ofthis invention is capable of extension to an extended area up to atleast 50% greater than its relaxed area. Moreover, the sheet material ofthis invention is characterized by having a substantially uniformquality and appearance in both the relaxed and extended states. Thepreferred sheet material of this invention is capable of extension to anextended area up to at least 100% greater than its relaxed area. Highlypreferred sheet material is capable of extension to an extended area upto at least 200% greater than its relaxed area.

As noted, the protective and decorative layer has a substantiallyuniform quality and appearance both in the relaxed and extended statesof the sheet material. This means that in the relaxed state the sheetmaterial is essentially free of coating defects such as lines, dimples,bubbles, streaks, banding, repellencies, colorant agglomerations and thelike when visually examined under roomlight, on a light box and insunlight. Furthermore, this means that the sheet material provides acommercially acceptable finish when applied to exterior automobilepanels. Moreover, a given relaxed size of sheet material can bestretched different degrees in different areas, or stretched in someareas and not in other areas and the uniformity of appearance in allareas, including distinctness of image, gloss, optical density, and flopremains substantially the same.

The sheet material of this invention preferably exhibits a distinctnessof image (DOI) of at least 80 as measured by ASTM TEST E-430. Suchmeasurements, for example, can be made on a HUNTERLAB MODEL D47R-6DORIGON GLOSSMETER. Preferred sheet materials of the invention exhibit aDOI of at least 85, and more preferably of at least 90 when measured bythis technique. Highly preferred sheet materials exhibit a DOI of atleast 95 when measured by this technique.

The sheet material of this invention preferably exhibits a high degreeof uniformity of optical density. Preferred sheet materials have a meanoptical density of at least 3.0. More preferably, they exhibit a maximumoptical density variation of less than 0.3 units from the mean densityof the sheet material as measured by an optical microdensitometer traceacross the width of the sheet material. Such measurements can be readilyobtained by those skilled in the art using conventional equipment, suchas a Perkin Elmer PDS Microdensitometer. Optical density is expressed bythe formula D=Log T wherein D is the optical density and T is the lighttransmittance. Optical density is conventionally used to express theamount of darkening on a photographic film because light differencesexpressed in density units closely reflect the manner in which the eyesees these differences. Thus, the lighter of two films that differ by0.3 density units transmits twice as much light as the darker. Highlypreferred sheet materials of this invention exhibit a maximum opticaldensity variation of less than 0.2 density units from the mean densityof the sheet material.

The sheet material of this invention preferably exhibits a 20° gloss ofat least 80 when measured in accordance with ASTM TEST D-2457.Particularly preferred sheet materials of this invention exhibit a 20°gloss of at least 85 and more preferably of at least 90 when measured bythis technique.

The sheet material of this invention preferably exhibits an averagesurface roughness (Ra) of less than 0.4 micron when measured byconventional surface roughness measuring techniques known in the art.For example, Ra can be measured using a scanning type stylus instrumenthaving a skidless probe and a cutoff of about 0.030 in. One suchinstrument is the Micro-Topographer® sold by Federal ProductsCorporation. Particularly preferred sheet materials of this inventionexhibit an average surface roughness of less than 0.2 micron and morepreferably of less than 0.1 micron.

In a highly preferred embodiment of this invention, as described in moredetail hereinafter, the protective and decorative layer includesreflective particles in addition to a colorant and binder. Any particlesconventionally employed in paints, particularly those employed inautomotive finish paints can be used. Suitable reflective particlesinclude metallic flakes such as aluminum flake, copper flake, bronzeflake, copper bronze flake, nickel flake, zinc flake, magnesium flake,silver flake, gold flake, platinum flake and other platelets such asmica, glass, stainless steel, coated mica, coated glass, and aluminumcoated polyester film fragments. Mixtures of two or more types ofparticles can be used.

The present invention also provides a process for the manufacture of thesheet material described above. This process comprises the steps ofproviding a flexible support sheet, providing a fluid protective anddecorative film-forming composition, forming a laminar flow of thecomposition and directing the flow into contact with the surface of thesupport to form thereon a protective and decorative layer ofsubstantially uniform thickness and converting the protective anddecorative coating to a dry and tack-free state. The fluid protectiveand decorative composition preferably comprises a film-forming binderand a colorant. In addition to the binder and colorant, the compositioncan include reflective particles and optionally other materials wellknown in the art of coatings. These would include surfactants, flowcontrol agents, thixotropic agents, fillers, organic solvents andcatalysts.

A variety of coating techniques are useful, such as direct extrusiononto the support by use of an extrusion hopper functioning to apply thecoating composition by a bead coating or a stretch-flow coatingmechanism, extrusion of the coating composition through a slot withsubsequent travel down the slide surface of a slide hopper or subsequentfree fall in a curtain coating process, curtain coating processes inwhich the curtain is generated by the use of an overflow weir, and soforth. The critical aspect of the coating process is its ability toprovide a defect-free coating with a very high degree of uniformity oflayer thickness. In view of the flexible nature of the support, it canbe coated using conventional web transport systems and will, for reasonsof economy, typically be coated at web widths of up to two meters ormore and web speeds of up to several hundred meters per minute.

The use of precision coating processes in the production of the sheetmaterial--such as for example the use of high precision extrusionhoppers--is a very important aspect of the present invention. Inparticular, the coating operation must be conducted with exactingcontrol of all critical parameters to ensure the very high degree ofthickness uniformity and the freedom from coating defects thatcharacterize the sheet material of this invention. It is only by suchcontrol of both thickness uniformity and coating defects, that sheetmaterial can be produced which is capable of undergoing the rigors ofthe thermoforming process and, at the same time, is capable of yieldinga product exhibiting the very high quality demanded of an automotivefinish.

Extrusion hoppers are particularly effective devices for use in theprocess of this invention. Such devices are well-adapted for use withcompositions which exhibit the shear-thinning characteristics typical ofthe paint compositions hereinbefore described. In such hoppers,transverse pressure gradients are minimized and almost all pressure dropacross the slot is in the direction of coating. While applicant does notwish to be bound by any theoretical explanation of the manner in whichhis invention functions, it is believed that such features contribute tothe excellent results achieved with an extrusion hopper, especially inthe coating of paint compositions containing reflective flakes.

Preferred coating techniques and apparatus useful in the practice of thepresent invention are used in the manufacture of photographic productsand are described in U.S. Pat. Nos. 2,253,060, 2,289,798, 2,681,294,2,815,307, 2,898,882, 2,901,770, 3,632,374, and 4,051,278.

After coating onto the support, the protective and decorativecomposition is converted to a dry and tack-free state, for example, bydrying by conventional techniques at temperatures of 25-100° C.

The process for manufacturing the sheet material of this invention on anindustrial scale can be carried out on apparatus of the type shown inFIG. 1. The support sheet is provided in a continuous web 10 which isunwound from supply roll 12 and passes around guide roller 14 and thenover coating roll 16. A take-up section can be provided to facilitateroll transfer. The support sheet is coated at the coating roll with thepaint layer as further described herein. After being coated, the supportsheet 10 passes through a series of drying chambers 20, 22, 24 and 26 ineach of which warm dry air is uniformly impinged on the coated layers toeffect drying thereof. The chambers 20, 22, 24 and 26 together define afirst drying zone, and since this zone can comprise additional similarchambers to provide a sufficiently long path of travel for web 10, theseries of chambers is illustrated as being broken at several places.After passing through the first drying zone, web 10 passes through asecond drying zone defined by chambers 30, 32 and 34. Since the seconddrying zone can comprise additional similar chambers to extend the pathof travel of web 10, this series of chambers is also illustrated asbeing broken at several places. The first drying zone functions to carryout the major portion of the drying of the coated layers, while thesecond drying zone serves to remove small amounts of residual liquidremaining in the coated layers. As illustrated, the drying chambers inthe first drying zone are of a flat-bed design while those in the seconddrying zone are of a festoon design in order to provide an extendedresidence time. After leaving the second drying zone, web 10 passesaround guide roll 36 and is wound onto take-up roll 38.

While the essential elements of the flexible and stretchable sheetmaterial of this invention are the support and the protective anddecorative layer, other optional layers can be included, and will beespecially beneficial under particular circumstances. For example, in apreferred embodiment the paint layer is coated on the support havingthereon an adhesion-promoting tie-layer which provides improved bondingstrength and thereby reduces the risk of delamination. Suitabletie-layers can be formed from compositions comprising an adhesionpromoting species and optionally a suitable solvent. Useful adhesionpromoting species include polymers derived from acrylonitrile,vinylidene chloride, and acrylic acid; polymers derived frommethylacrylate, vinylidene chloride and itaconic acid; cellulosenitrate, and a variety of commercially available adhesion promotingspecies, for example, those known under the trade designations FORMVAR7/95, FORMVAR 15/95, BUTVAR B-98 and BUTVAR B-72, sold by Monsanto,MOBAY M-50 sold by Mobay, VINAC B-15 sold by Air Products, ELVACITE soldby DuPont, and LEXAN sold by General Electric. Suitable solvents includemethylethyl ketone, methylene chloride, tetrahydrofuran, toluene, methylcellosolve, methanol, ethanol, propanol, butanol, mixtures thereof andthe like. The adhesion promoting layer preferably has a thickness notgreater than about 0.0025 millimeter. The thickness preferably issubstantially less than the thickness of the decorative and protectivelayer. For example, the protective and decorative layer preferably has athickness at least 8 times the thickness of the adhesion promotinglayer.

As noted, a particularly important use for the sheet material relates toits application to exterior automotive panels, whereby the need forspray painting in the manufacture of automobiles can be reduced oreliminated. The sheet material including a substantially clear layer,also referred to herein as a topcoat, adhered to the protective anddecorative layer is particularly useful in providing high qualityexterior automotive finishes. A topcoat can be incorporated at theoutermost layer of the sheet material of this invention. The topcoat andprotective and decorative layer can comprise separate strata or a singlestratum. The topcoat can provide such desired properties as improvedsmoothness, high gloss, hardness, durability, resistance to weathering,abrasion resistance, resistance to scratching, chipping and marring, andresistance to spot damage caused by acid rain or pollution.

Topcoat compositions for use with basecoat compositions are well knownin the art. They are generally transparent and can comprisecrosslinkable polyols such as polyester polyols, polyurethane polyolsand acrylic polyols, and polyisocyanate curing agents. In accordancewith a preferred embodiment of this invention, the clear layercomposition is extruded through a slot onto the paint layer of the sheetmaterial. This advantageously results in improved smoothness, excellentgloss and distinctness of image, compared to topcoats applied byconventional spraying techniques. The clear layer is then converted to adry and tack-free state, for example by drying by conventional dryingtechniques at temperatures of 25-100° C.

Alternatively, the topcoat and basecoat compositions can be coated as aunitary stratum from one coating composition, or can be coatedsimultaneously using known techniques, for example, those described inU.S. Pat. Nos. 2,761,791, 2,941,898, 3,206,323, 3,425,857, 3,508,947,3,645,773 and 4,001,024. Furthermore, it is possible to lay down two ormore layers, for example by multiple layer extrusion, of a multi-layersheet material before drying, instead of drying each layer individuallybefore laying down the next layer.

In a particularly preferred embodiment of the invention the support,basecoat layer and topcoat layer have heat softening and tensileelongation properties which render the sheet material suitable for usein the thermoforming process and which are mutually compatible so as topermit symmetrical elongation, whereby the sheet material can undergosubstantial elongation by the application of stretching forces withoutcrazing or delamination of the basecoat and topcoat layers. The support,basecoat layer and topcoat layer preferably are of sufficiently uniformcharacter that the sheet material exhibits substantially the sameuniformity of appearance before and after the thermoforming process.

The elongation properties of the topcoat must be compatible with thoseof the sheet material in the thermoforming process. The sheet materialincluding the clear layer must be able to undergo substantial elongationby the application of stretching forces without splitting of the topcoatnor delamination of the topcoat from the adjacent layer. Furthermore,the topcoat preferably is formulated to minimize adverse effects onappearance, i.e., gloss, which can occur upon application of thestretching forces. The appearance, gloss, durability and resistance toweathering of the topcoated protective and decorative coatings of thepresent invention can at least equal or exceed that achieved with aspray painting process.

The present invention has the advantage that basecoat and topcoat paintsconventionally used as automotive finishes are made available in theform of a pre-formed sheet material which is thermoformable and whichcan be permanently bonded to exterior parts of automobiles, such asfenders or doors, to provide a protective coating having properties atleast as good as those attainable by the costly, laborious and wastefulprocess of spray painting that has heretofore been used in applying suchcoatings. The invention has the further advantage of enhanced capabilityto provide the "high stylistic effects" that are achievable withmetallic paint layers characterized by great "depth" and a high degreeof geometric metamerism. Another advantage of the present invention isthat it provides the flexibility for rapid color changes in the processof manufacturing the sheet material and in the process of applying thematerial to automobile parts. A further advantage of this invention isthe ability to control color uniformity which is particularly desirablewhen colors have to be matched. Furthermore, the invention can provide,if desired, multi-tone and/or multi-color sheet materials, and sheetmaterials having a controlled textured surface.

Paint compositions comprising metallic particles and colorants are knownto provide an overall aesthetically pleasing impression on the viewerand thus are useful in providing decorative coatings, particularly uponthe surface of automobile bodies. Such coatings accentuate the stylinglines and contoured surface and are characterized by what is known asgeometric metamerism. Geometric metamerism, also referred to asgoniochromatism or "flop", is the ability of a paint film to exhibitsubtle variations in color and appearance depending upon directions fromwhich it is viewed. This effect is produced by metal flakes incorporatedinto the film at varying depths. Light traveling through the film isreflected by the flakes to a viewer. For a paint film also containing acolorant, the degree of color or hue depends upon the distance traveledby the light through the film such that a viewer perceives a combinationof light rays having different degrees of color. Further, the distancetraveled by light rays reflected off the flakes depends upon the angleof incidence and angle of reflection. Light traveling normal to theflake surface travels a shorter distance than light traveling at acuteangles. The combination of these phenomena makes a film having geometricmetamerism appear to be brighter and have a lighter hue when viewednormal to its surface than when viewed at an acute angle. Thus, a viewerlooking directly down upon the film surface observes a light, brightcolor. Flakes near the film surface reflect light that only slightlyinteracts with the colorant and so appear to sparkle. When the viewershifts to look at the film at an acute angle to its surface, a darker,more intense color is perceived. Because of the greater degree ofinteraction, less sparkling is observed and the film appears generallydeeper or thicker. At angles approaching the plane of the film surface,multiple reflections between metal flakes dramatically increase thelight-colorant interaction making the film appear extremely dark anddeep.

The spray coating process is conventionally utilized as a means oforienting reflective flakes to provide protective coatings exhibiting ahigh degree of geometric metamerism. However, this process suffers fromserious disadvantages. It requires the use of compositions which have alow viscosity which is achieved by the use of a high percentage ofsolvent. The low viscosity low solids formulations are highlydisadvantageous because of the need to remove large quantities oforganic solvents in the drying operation. As a consequence, a prolongeddrying step is necessary to remove the solvent. It would be verydesirable to form protective coatings exhibiting a high degree ofgeometric metamerism from high viscosity compositions that containrelatively low percentages of solvent and, accordingly, could be quicklydried. However, such a high viscosity coating composition would not beamenable to spraying. Moreover, in the low viscosity compositions thatare conventionally spray coated, the orientation takes place during thedrying step as a result of leveling and shrinkage forces. Effectiveoperation of these forces would be severly inhibited by the use of highviscosity compositions.

A particularly advantageous feature of the present invention is that itis no way dependent on the use of low viscosity low solids formulations,but can readily accommodate the use of high viscosity high solidscompositions and even permit the elimination of solvents entirelythrough the use of radiation-curable coating compositions which aretotally convertible to a solid form. Further, reflective particles whichare too large to be incorporated in sprayable paint compositions can bereadily coated by the method of this invention. Furthermore, control ofsolvent emission problems is made much easier by the ability to coataqueous or mixed aqueous/organic systems rather than organic systems, bythe ability to coat very high solids compositions, by the ability toeliminate solvent emission entirely through the use of radiation-curableformulations that are fully convertible to a solid form, and by theinherently much greater simplicity in controlling solvent emissions in aweb coating operation as contrasted with a spray painting operation.

Moreover, the present invention can provide a sheet material having anextremely high degree of geometric metamerism which is surprising andunexpected. The reason for this is not completely understood at thistime. It is believed that this superior effect is due at least partly tothe high concentration and degree of uniformity of distribution of thecolorant and light-reflecting particles in the protective and decorativelayer, which uniformity is superior to that achieved with conventionalspraying techniques. Further, the light-reflecting particles exhibitorientations substantially parallel to the outer surface of theprotective and decorative layer. For example, as illustrated in FIG. 5,protective and decorative layer 42 preferably contains generally flatparticles 44 comprised of a light-reflecting material such as mica or ametal. The particles have a preferred orientation with their flat faceswithin 0-12 degrees of parallelism with outer surface 46. At least 75%,more preferably 80%, of the flakes are in the preferred orientation withsubstantially none of the particles having an orientation greater thanabout 50°. This is illustrated by the metal flake histogram of FIG. 6.The uniformity of particle angle orientation attained is also surprisingand unexpected to those skilled in the art, particularly in view of thethickness of the layers involved.

The present invention provides many additional important benefits in thefield of automotive finishes. For example, the same sheet material canbe used to form decorative and protective coatings on both rigid metalparts and flexible plastic parts of an automobile and accordingly, byuse of the identical material for both types of parts, can eliminateproblems of color matching. This is much more difficult to do with spraypainting, since paints which are suitable for application to rigid metalparts are generally not suitable for application to flexible plasticparts so that two different types of paint have to be used.

Furthermore, the present invention is capable of widespread applicationin many other industrial manufacturing operations--wherever it isdesired to provide protective and decorative coatings of very highquality. For example, the sheet material of this invention findsparticular utility in products such as office equipment, householdappliances, automobile bumpers, auto interior and trim parts, and cameraand apparatus housings.

The sheet material described above can be bonded to variousthree-dimensional substrates through use of well known vacuum-formingand thermoforming techniques to provide a structural element inaccordance with this invention. The sheet material provides a uniformwrinkle-free protective coating which has an appearance at least as goodas or better than that which is achieved by conventional spray paintingtechniques.

Thus, in accordance with the invention there is provided a method ofapplying a protective and decorative coating on a three-dimensionalsubstrate, which method comprises the steps of (1) providing athree-dimensional substrate to which a protective and decorative coatingis to be applied; (2) providing the flexible and stretchable sheetmaterial described above; and (3) simultaneously heating and stretchingthe sheet material as it is brought into conforming association with atleast one surface of said substrate and securely bonding it to saidsubstrate to form thereon a smooth and wrinkle-free protective anddecorative coating.

The substrate can be rigid or deformable. Rigid substrates includesubstrates composed of sheet metal, synthetic resins, etc. Elementscomprised of such substrates find particular utility as components of anautomobile body. Deformable substrates include substrates subject toimpacts. One such use is for impact-absorbing bumpers used inautomobiles.

In a method of this invention, the sheet material is made soft andflowable by application of heat and is then brought into conformingcontact with the article to be coated and is securely bonded thereto.For example, the sheet material can be heated to a temperature withinabout 25° C. of the glass transition temperature of the support. Suchbonding can be effected by the use of well known adhesive bondingtechniques using any of a wide variety of suitable adhesivecompositions. The adhesive can be provided by known means on the side ofthe support opposite to the protective and decorative layer. Theadhesive facilitates bonding of the sheet material to the substrate. Ininstances where an adhesive backcoat is applied, the web is interwoundwith a release sheet to permit it to be wound on a core. Suitableadhesives include acrylic resins and known shrink wrap adhesives. Asuitable release sheet comprises a thin polyester film having a siliconerelease layer thereon.

This invention also provides a method of molding a shaped article andsimultaneously providing such article with a protective and decorativecoating which method comprises the steps of providing a mold in theconfiguration of the shaped article; positioning within the mold theabove-described flexible and stretchable sheet material, injecting intothe mold a fluid composition which is capable of hardening to both formthe desired shaped article and bond to the sheet material; and removingfrom the mold a shaped article having a protective and decorativecoating formed from the sheet material securely bonded thereto. Forexample, the sheet material can be integrally bonded to a moldedelastomeric article. In this instance, the sheet material is placed in amold cavity, and an elastomeric molding compound, such as a urethanerubber, is injected into the mold cavity under pressure against the sideof the support opposite the light-reflecting layer to stretch the sheetmaterial so it conforms to the shape of the molded article and bonds tothe outer surface of the article. Suitable molds, hardenable fluidcompositions and molding process parameters for this method arewell-known and form no part of the present invention.

The sheet material of this invention preferably has a heat deformationtemperature or softening point that is sufficiently low that it can bethermoformed at temperatures that do not adversely affect the propertiesof the protective and decorative layer or other layers. On the otherhand, when a crosslinkable clear topcoat layer that is cured byapplication of heat is employed, the softening point of the sheetmaterial should be sufficiently high as to permit such curing withoutadversely affecting the physical properties of the sheet material. Thus,in some instances, there may be only a relatively narrow operatingwindow between the temperature at which the sheet material is cured, andthe higher temperature at which it is thermoformed. The softening pointof the sheet material must, of course, also be sufficiently high toresist the temperatures which the end product encounters in use withoutphysical distortion or damage. For example, when used as a protectiveand decorative coating on the exterior surfaces of an automobile, thesheet material may be subjected to relatively high temperatures when theautomobile is parked outdoors on a hot, sunny day.

EXAMPLES

The following examples further illustrate the invention.

EXAMPLE 1

A support sheet was prepared from a blend described in U.S. Pat. No.4,582,876 as follows.

A mixture of 55:45% by weight of polyester (1) and Dylark® StyreneCopolymer 600 was compounded by extrusion. Polyester (1) was derivedfrom terephthalic acid, 19 mole % ethylene glycol and 81 mole %1,4-cyclohexanedimethanol. Dylark® Styrene Copolymer 600 is a rubbermodified styrene-maleic anhydride copolymer available from ARCO ChemicalCompany, a division of Atlantic Richfield Company.

The blend was heated to 260-290° C. and extruded through a die into anip comprising two temperature controlled chrome plated stainless steelrollers. The extruded web was then cooled on a chill roller. Thethermoplastic support had a mean thickness of about 0.20 millimeters anda maximum thickness deviation of less than 0.02 millimeters.

The support sheet prepared as described above was provided with atie-layer comprising a polymer derived from acrylonitrile, vinylidenechloride and acrylic acid (mole ratio 15:65:20) as the adhesionpromoting species. A coating composition comprising the polymer at 11/2%solids in MEK at room temperature was extrusion coated through a 0.13millimeter slot and dried at 40-90° C. to a coverage of 215 ^(mg) /m².

The composition of Table 1 below was metered from a nitrogen gaspressurized vessel through an extrusion slot having a width of 0.25millimeter onto the support prepared and treated as described above at aspeed of 8 ^(m) /min. The coating was dried at 40-90° C. (dry coverage43 ^(gm) /m²). The coating roll was cooled with recirculating water toreduce the propensity of the coating to streak and to minimizeprecipitate formation on the hopper lip. The coating method andapparatus is described in U.S. Pat. No. 2,681,294 and included means formaintaining a pressure differential across opposite surfaces of thecoating ribbon.

                  TABLE 1                                                         ______________________________________                                        Ingredient          Approximate % Weight                                      ______________________________________                                        Deionized water     50                                                        Urethane resin      25                                                        Aluminum paste      5                                                         Ethylene Glycol Monohexyl Ether                                                                   5                                                         N-Methylpyrrolidone 5                                                         Diethylene Glycol Monobutyl Ether                                                                 1                                                         N,N-Dimethyl Ethanolamine                                                                         1                                                         Xylene              1                                                         Aliphatic Solvent Naphtha                                                                         1                                                         Isopropyl Alcohol   <1                                                        ______________________________________                                    

Thereafter, the protective and decorative layer thus formed was providedwith a clear layer thereover comprising components A and B identified inTABLE 2 below.

                  TABLE 2                                                         ______________________________________                                        Ingredient          Approximate % Weight                                      ______________________________________                                        A   Urethane Resin      60                                                        Toluene             30                                                        2-Butoxy Ethyl Acetate                                                                            10                                                        Benzotriazole        1                                                    *B  Polyfunctional aliphatic                                                                          100                                                       isocyanurate resin based on                                                   1,6-hexamethylene diisocyanate                                            ______________________________________                                         *Available as Desmodur N3000 from Mobay Corporation Coatings Division.   

Composition A diluted to 58% solids with toluene and composition Bdiluted to 85% solids with acetone were mixed and coated onto thelight-reflecting layer at 4 ^(m) /min and dried at 40-90° C. for 6minutes to form a clear topcoat having a thickness of 0.06 millimeters.The dry coverage of composition A was 51 ^(gm) /m². The dry coverage ofcomposition B was 13 ^(gm) /m².

The sheet material thus prepared exhibited a high level of uniformity oflayer thickness, an ability to undergo substantial elongation, and ahigh degree of resistance to flexural cracking. Moreover, the materialexhibited a uniform optical density, excellent gloss, surface smoothnessand distinctness of image, and an unusually high degree of geometricmetamerism. Further, the material could be elongated 150% by applicationof heat and simultaneously stretched while achieving a defect-freecoating of uniformly attractive appearance.

EXAMPLES 2-4 Use of Other Paint Compositions

Example 1 was substantially repeated except that the protective anddecorative layer was formed from the composition of Table 3 below.

                  TABLE 3                                                         ______________________________________                                        Ingredient          Approximate % Weight                                      ______________________________________                                        Deionized water     55                                                        Urethane resin      20                                                        Ethylene Glycol Monohexyl Ether                                                                   5                                                         N-Methylpyrrolidone 5                                                         Diethylene Glycol Monobutyl Ether                                                                 1                                                         N,N-Dimethyl Ethanolamine                                                                         1                                                         Titanium Dioxide/Mica                                                                             <1                                                        Silica              <1                                                        Carbon Black        <1                                                        Isopropyl Alcohol   <1                                                        ______________________________________                                    

The sheet material exhibited a substantially uniform quality appearancewhich was an acceptable exterior automotive finish. A non-metallic blackpaint composition (43 ^(gm) /m²) and a white paint composition (64 ^(gm)/m²) yielded acceptable results.

EXAMPLES 5-8 Use of Different Tie-Layer Composition

Examples 1-4 were repeated expect that the tie-layer compositiondescribed in Table 4 was employed. The composition of Table 4 (17%solids) was diluted to 5% solids with water and coated to a dry coverageof 0.54 ^(gm) /m² (dry thickness 0.0005-0.0010 millimeters). Theappearances of Examples 5-8 with this tie-layer were similar to Examples1-4, respectively.

                  TABLE 4                                                         ______________________________________                                        Ingredient          Approximate % Weight                                      ______________________________________                                        Deionized water     75                                                        Acrylic Resin       10                                                        Urethane resin      10                                                        N-Methylpyrrolidone 1                                                         Diethylene Glycol Monobutyl Ether                                                                 1                                                         Ethylene Glycol Monohexyl Ether                                                                   <1                                                        N,N-Dimethyl Ethanolamine                                                                         <1                                                        FC 170 Surfactant, sold by 3M Co.                                                                 ˜0.05                                               ______________________________________                                    

It will be appreciated, from the foregoing detailed description andworking examples, that by reason of the physical parameters of the novelsheet material described herein, the many problems inherent in providinghigh quality decorative and protective coatings on shapedthree-dimensional substrates have been solved in an efficient andeffective manner which readily lends itself to high volume low costcommercial operation.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

What is claimed is:
 1. A process for the manufacture of a flexible andstretchable sheet material adapted for use in a thermoforming process inwhich it is stretched to conform to a three-dimensional substrate andbonded thereto so as to form a smooth and wrinkle-free protective anddecorative coating thereon, said process comprising the steps of:(1)providing a thin, essentially planar, stretchable, thermoplasticpolymeric support of substantially uniform thickness; (2) providing afluid paint composition comprising a film-forming binder and a colorant;(3) forming a laminar flow of said paint composition and directing saidflow into contact with the surface of said thermoplastic polymericsupport to form thereon a thin paint layer of substantially uniformthickness; and (4) converting said paint layer to a dry and tack-freestate.
 2. The process of claim 1 wherein said laminar flow is formed byextruding said composition through a slot.
 3. A process according toclaim 1, wherein said paint layer has an outer surface and containsgenerally flat light reflecting particles having a preferred orientationwithin 12 degrees of parallelism with said outer surface, and at least75% of said particles being in the preferred orientation.
 4. A processaccording to claim 3, wherein substantially none of the particles havean orientation greater than about 50° of parallelism.
 5. A processaccording to claim 1 further comprising:providing an adhesion promotinglayer between said support and said paint layer.
 6. A process accordingto claim 5, wherein said paint layer is at least 8 times the thicknessof said adhesion promoting layer.
 7. A process according to claim 5,wherein said adhesion promoting layer has a thickness not greater thanabout 0.0025 millimeters.
 8. A process according to claim 1 furthercomprising:providing a substantially clear layer adhered to said paintlayer.
 9. A process according to claim 8, wherein said clear layer has athickness substantially greater than said paint layer.
 10. A processaccording to claim 1, wherein said paint layer provides a distinctnessof image of at least
 80. 11. A process according to claim 1, whereinsaid paint layer has a 20° gloss of at least
 80. 12. A process accordingto claim 1 further comprising:providing a pressure sensitive adhesivelayer on the opposite side of said support sheet from said paint layer.13. A process according to claim 1, wherein said support has a meanthickness ranging from 0.05 to 0.40 millimeters.
 14. A process accordingto claim 13, wherein said support has a maximum thickness deviation fromits mean thickness of less than 20%.
 15. A process according to claim 1,wherein said paint layer has a mean thickness ranging from 0.012 to0.080 millimeters.
 16. A process according to claim 1, wherein saidsheet material has a thickness ratio for said paint layer to saidsupport which ranges from 1.00 to 0.04.
 17. A process according to claim1, wherein said sheet material has an optical density of at least
 3. 18.A process according to claim 17, wherein said sheet material has maximumoptical density variation of less than 0.3.
 19. A process according toclaim 1, wherein said sheet material has an average surface roughness ofless than 0.4 microns.
 20. A process according to claim 1 furthercomprising:providing a substrate to which said support of said sheetmaterial is bonded.